1. Field of the Invention
This invention relates to the unsaturated aldehyde 2-propyl-pent-4-en-1-al of the formula ##STR2## and a process for preparing the same.
2. Discussion of the Prior Art
Pent-4-en-1-al and various substitution products of this unsaturated aldehyde are known from the literature. German Auslegeschrift No. 25 17 447 describes the preparation of pent-4-en-1-al from an acetaldehyde acetal containing at least one allyl alcohol radical. In accordance with the known procedure, the acetal is passed at 350.degree. to 450.degree. C. in the gaseous phase over a surface-active catalyst. Under the reaction conditions a mol of allyl alcohol splits off, and the doubly unsaturated ether thereby formed rearranges to pent-4-en-1-al.
The preparation of substituted pent-4-en-1-als is the subject of a publication by Kent C. Brannock in J. Am. Chem. Soc. 81 (1959), 3382. Aldehyde diallylacetals are used as starting materials, from which one mol of allyl alcohol is split off under the catalytic effect of acid. Allyl alkenyl ethers are formed, which can rearrange to form the substituted 4-pentenals without previously having been isolated.